Recently, License Assisted Access (LAA) has been proposed as a solution for offloading a licensed spectrum, such as e.g. Long-Term Evolution (LTE) by using an unlicensed, “free” spectrum, for instance LTE in unlicensed spectrum (LTE-U), or the 2.4 GHz or 5 GHz band used by Wi-Fi equipment.
With LAA, initial access is made on a licensed spectrum (e.g. LTE) primary carrier, but the traffic load is then shared on an unlicensed spectrum (e.g. LTE-U or Wi-Fi) secondary carrier, using known methods such as Carrier Aggregation (CA) or Dual Connectivity (DC). Hence, the unlicensed spectrum is used for transferring bulk payload data of a mobile terminal on the secondary carrier, while control of the mobile terminal still is maintained in the licensed spectrum via the primary carrier.
When LAA is used to serve e.g. indoor traffic (or an outdoor hotspot) provisioned by for instance a picocell, the licensed spectrum indoor cell might not cover the entire building—sections of the building may be covered by an outdoor macro cell. In fact, even if the unlicensed spectrum controlled by the indoor cell covers the entire building, there may still be sections in the building where the outdoor macro cell is stronger than the indoor cell and thus acts as a serving cell for some of the indoor mobile terminals
This may cause problems, in that indoor mobile terminals may establish communication channels with an outdoor base station of the macro cell instead of connecting to an indoor base station. As discussed hereinabove, using LAA, an unlicensed spectrum carrier may be set up with the indoor base station. However, the current LAA approach may lead to poor utilization of system resources, in particular causing an unnecessary load on macro cells in the case where the macro cells are to be offloaded by smaller cells, such as indoor systems.